At a running club, 30% of the members are male. 60% of the male members and 50% of the female members are training to run a marathon. Without using a calculator, work out what percentage of the members are training for a marathon.
Let's assume the running club has 100 members.
If 30% of the members are male, we have 30 members.
Out of these 30 members, 60% are training for a marathon, which is 0.6 * 30 = <<0.6*30=18>>18 members.
The remaining 70% are female, so we have 70 members.
Out of these 70 members, 50% are training for a marathon, which is 0.5 * 70 = <<0.5*70=35>>35 members.
Therefore, the total number of members training for a marathon is 18 + 35 = <<18+35=53>>53 members.
Finally, the percentage of members training for a marathon is (53/100) * 100 = <<(53/100)*100=53>>53%. Answer: \boxed{53}.